Manganese ferrite oxidative dehydrogenation catalysts

ABSTRACT

THE PRESENCE OF 1 TO 20 WEIGHT PERCENT CARBON BLACK IN A MANGANESE FERRITE OXIDATIVE DEHYDROGENATION CATALYST IMPROVES THE YIELDS FROM OXIDATIVE DEHYDROGENATION REACTIONS EMPLOYING SUCH CATALYST. THE PRESENCE OF ABOUT 5 WT. PERCENT CARBON BLACK IN A MANGANESE FERRITE CONTAINING CHROMIUM AS A PROMOTER RESULT IN UP TO 7.3% ABSOLUTE INCREASE IN YIELD IN THE OXIDATIVE DEHYDROGENATION OF ISOAMYLENE AS COMPARED TO THE CATALYST PREPARED UNDER THE SAME CONDITIONS WITHOUT CARBON BLACK.

United States Patent O 3,751,385 MANGANESE FERRITE OXIDATIVE DEHYDRO-GENATION CATALYSTS Harold E. Manning, Houston, Tex., assignor to Petro-Tex Chemical Corporation, Houston, Tex. No Drawing. Filed Oct. 7, 1970,Ser. No. 78,956 Int. Cl. B01j 11/22, 11/26; C07c /18 US. Cl. 252-447 8Claims ABSTRACT OF THE DISCLOSURE This invention relates to oxidativedehydrogenation of organic compounds having at least one ii I I Moreparticularly the invention relates to the use of manganese ferritecatalyst in such oxidative dehydrogenation. Specifically the inventionrelates to manganese ferrite catalysts prepared in a particular manner.

It is known to dehydrogenate organic compounds by contacting thecompounds to be dehydrogenated at an elevated temperature preferably inthe presence of catalysts. One method of dehydrogenation is known asoxidative dehydrogenation. According to this process, hydrogen releasedfrom the organic compounds reacts with oxygen to form water. One of theprincipal defects in oxidative dehydrogenation reactions is that quiteoften the reactions are unselective and oxygenated compounds are formedinstead of the desired dehydrogenated compounds. These non-selectivereactions are particularly evident when the compound to bedehydrogenated contains three or more carbon atoms. For example, whenmethyl butene is reacted with oxygen, a variety of products other thanisoprene are possible as hydrocarbons and oxygenated hydrocarbons ofvarious general mixtures may result. Also, combustion of the hydrocarbonmay result in the formation of C0, C0 and water.

It is therefore one of the principal objectives of this invention toprovide a process and catalyst wherein the organic compound isdehydrogenated preferably to a product having the same number of carbonatoms at a high level of conversion and selectivity. Another principalobjective is to provide a process wherein the catalyst has long catalystlife. Other objectives of this invention are to provide a processwherein it is possible to have substantial quantities of steam presentin the dehydrogenation zone, a high over-all throughput and a lowcontact time in the dehydrogenation zone and a process which has goodcontrol of reaction temperature. These and other objectives may beachieved by the process of this invention.

Briefly stated, one aspect of the present invention is an oxidativedehydrogenation catalyst comprising a manganese ferrite containing aminor amount of carbon black. Generally the manganese ferrite willcontain from about .1 to 20 weight percent of carbon black based on theother catalyst components preferably about 1 to 15 weight percent andmore preferably about 2 to 10 weight percent.

Patented Aug. 7, 1973 In addition to carbon black catalyst bindingagents or fillers may be used, but the carbon black and said binders andfillers will not ordinarily exceed about 50 percent or 60 percent byweight of the catalysts and the described catalytic compositions willpreferably constitute the main active constituent. These binding agentsand fillers will preferably be essentially inert. Preferred catalystsare those that have at least 25 or preferably 50 weight percent of thedefined catalyst actives. Also preferably iron will constitute at least50 atomic weight percent of the cations in the catalyst. Unless statedotherwise, the compositions in this application are the main activeconstituents of the dehydrogenation process during dehydrogenation andany ratios and percentages refer to the surface of the catalyst incontact with the gaseous phase during dehydrogenation.

The catalysts of this invention comprise manganese ferrite produced in aparticular manner. Manganese ferrite comprises a complex crystallinestructure comprising manganese, iron and oxygen. According to thisinvention superior catalysts can be formed by producing the manganeseferrite by reacting the precursors of the manganese ferrites after theprecursors have been intimately mixed with carbon black.

Manganese ferrite formation may be accomplished by reacting an activecompound of iron with an active compound of manganese. By activecompound is meant a compound which is reactive under the conditions to.form the ferrite.

The starting materials may be such as oxides, hydroxides, or saltsincluding oxal-ates, acetates, formates, sulfates, nitrates, halides,hydrates and so forth. Suitable manganese compounds are such asmanganese oxalate, manganese hydroxide, manganese nitrate, manganesecarbonate, manganese salts of aliphatic monocarboxylic acids of 1 to 5carbon atoms, manganese sulfates, salts of aliphatic alcohols of l to 5carbon atoms, hydrates thereof and mixtures thereof. The same classes ofiron compounds may be employed such as iron nitrate, etc. The inorganicsalts give excellent results.

The iron and manganese precursor components and carbon black can becombined in any conventional manner which will provide an intimatemixture, for example, manganese oxide, iron oxide and carbon black canbe mixed in a slurry or dry mixed. One component can be deposited onanother or the precursor components can be coprecipitated.

One procedure for forming the catalysts is to prepare an aqueous mixtureof the precursor salts and thereafter this mixture can then beprecipitated by mixing with a basic reactant to precipitate theprecursor of the ferrite. Any suitable base may be employed but thosecontaining unwanted cations will, of course, be less desirable. Volatilebases such as ammonium hydroxide or carbonate may be employed.

The temperature used for ferrite formation may be varied, dependingsomewhat upon the particular starting materials and upon the conditionspresent during ferrite formation. At any rate, superior catalysts areproduced at temperatures of from high enough to form the ferrite to 800C. or less. Still better catalysts are ordinarily pro duced attemperatures of less than 700 C. Suitable temperatures of reaction aresuch as between about 400 to 800 'C. with 10 a preferred range beingfrom between about 500 to 700 C.

Another factor in producing superior catalysts is the rate of heating ofthe reactants to form the ferrite. Here again the rate of heating willbe dependent upon the particular react-ants and conditions employed, butbetter results are generally obtained when the reactants are heated at arate of no greater than about 250 C. per

minute and still better results are ordinarily obtained when the rate isno greater than about 100 C. per minute.

The ferrites are preferably prepared in an atmosphere containing littleor no oxygen. Preferably the atmosphere will contain less oxygen thanair, i.e., less than about mole percent oxygen. More preferably thecalcining atmosphere will be substantially free of oxygen. Suitableatmospheres are gases such as nitrogen, helium, argon, neon, krypton,xenon and the like or mixtures thereof.

Improved manganese ferrite compositions may be obtained by utilizinghalogen or halogen compounds during the formation of the ferrite. Theuse of halogen or halogen compounds in this manner is claimed in acopending application by Philip M. Colling and Johnny C. Dean, Ser. No.671,236, now Pat. 3,567,793, issued Mar. 2, 1971, entitled OxidativeDehydrogenation of Organic Compounds. An example of the use of a halogenwould be the addition of manganese chloride to the reactants prior tothe formation of the ferrite. Normally, chlorine is the preferredhalogen so used.

The manganese ferrite compositions of this invention may also compriseadditives. Phosphorus, silicon or mixtures thereof are examples ofadditives. For instance, phosphorus and/or silicon may suitably bepresent in an amount of from about 0.2 to weight percent based on thetotal weight of the atoms of iron and manganese. These ingredients maycontribute e.g. to the stability of the compositions. The silicon,phosphorus or other additives may be added at various stages of thepreparation of the composition, or may be added to the already formedmanganese ferrite. Any suitable compounds may be employed such asphosphoric acid, phosphorus pentoxide, ethyl phosphate, ammoniumphosphate, silicon halides, etc.

It has been found that a particularly useful manganese ferrite is onethat contains a small amount of chromium in the crystalline lattice. Upto about 0.4 atom of chromium per atom of manganese may be used,preferably about 0.05 to 0.2 atom. The chromium is incorporated intoferrite preferably by combining a reactive chromium compound with thereactive iron and manganese compounds and carbon black prior to reactingto form the ferrite. Suitable reactive materials are chromium oxide,chromium oxalate, chromium acetate, chromium sulfate and the like, aspreviously described for the iron and manganese starting material.

The manganese ferrite compositions may be reduced with a reducing gasprior to use in the process of dehydrogenation. Examples of reducinggases are hydrogen or hydrocarbons. For example, the manganese ferritecompositions may be reduced with e.g. hydrogen at a temperature of atleast 250 C. with the temperature of reduction generally being nogreater than 850 C. By reducing gas is meant a gas that will react withoxygen under the conditions of reduction. However, it is one of theadvantages of this invention that the manganese ferrites preparedaccording to this invention may not require reduction prior to use inthe dehydrogenation reaction.

According to this invention it has been found that the preferredmanganese ferrite compositions exhibit a certain type of X-raydiffraction pattern. The preferred compositions do not have as sharpX-ray diffraction reflection peaks as would be found, e.g., in a highcrystalline material having the same chemical composition. Instead, thepreferred catalyst of this invention exhibit reflection peaks which arerelatively broad. The degree of sharpness of the reflection peak may bemeasured by the reflection peak band width at half height (Wh/2). Inother words, the width of the reflection peak as measured at one-half ofthe distance to the top of the peak is the band width at half height.The band width at half height is measured in units of 2 theta.Techniques for measuring the band widths are discussed, e.g., in Chapter9 of Klug and Alexander, X-ray Diffraction Procedures, John Wiley andSon, N.Y., 1954.

According to one theory of manganese ferrite preparation it isconsidered that maintenance of the manganese precursor in the +2 valancestage during the formation stage of the ferrite contributes to superiorcatalytic properties. Under this assumption it can be further theorizedthat carbon black acts as an oxygen scavenger to help maintain the +2 ofthe manganese. As stated before the mechanism is merely suppositive andalthough it may be of aid to those skilled in this art in understandingthe invention, no reliance is placed thereon for patentability, nor isit intended that the instant invention or any derived herefrom be in anyway limited or restricted because of such theoretical mechanisms.

The process of this invention may be applied to the dehydrogenation of agreat variety of organic compounds to obtain the correspondingunsaturated derivative thereof. Such compounds normally will containfrom 2 to 20 carbon atoms, at least one l I a boiling point below about350 C., and such compounds may contain other elements, in addition tocarbon and hydrogen such as oxygen, halogens, nitrogen and sulphur.Preferred are compounds having from 2 to 12 carbon atoms, and especiallypreferred are compounds of 2 to 6 or 8 carbon atoms.

Among the types of organic compounds which may be successfullydehydrogenated to the corresponding unsaturated derivative by means ofthe novel process of this invention are nitriles, amines, alkyl halides,ethers, esters, aldehydes, ketones, alcohols, acids, alkyl aromaticcompounds, alkyl heterocyclic compounds, cycloalkanes, alkanes, alkenes,and the like. Illustration of dehydrogenations include propionitrile toacrylonitrile, propionaldehyde to acrolein, ethyl chloride to vinylchloride, methyl isobutyrate to methyl methacrylate, 2 or3-chl0robutene-1 or 2, 3-dichlorobutane to chloroprene, ethyl pyridineto vinyl pyridine, ethylbenzcne to styrene, isopropylbenzene to a-methylstyrene, ethylcyclohexane to styrene, cyclohexane to benzene, ethane toethylene, propane to propylene, isobutane to isobutyle, n-butane tobutene and butadiene-1,3, butene to butadiene-1,3 and vinyl acetylene,methyl butene to isoprene, cyclopentane to cyclopentene andcyclopentadiene-1,3, n-octane to ethyl benzene and ortho-xylene,monomethylheptanes to xylenes, propane to propylene to benzene, ethylacetate to vinyl acetate, 2,4,4-trimethylpentane to xylenes, and thelike. This invention may be useful for the formation of new carbon tocarbon bonds by the removal of hydrogen atoms such as the formation of acarbocyclic compound from two aliphatic hydrocarbon compounds or theformation of a dicyclic compound from a monocyclic compound having anacyclic group. Examples of conversions are the conversion of n-heptaneto toluene and propene to diallyl. Representative materials which aredehydrogenated by the novel process of this invention include ethyltoluene, alkyl chlorobenzenes, ethyl naphthalene, isobutyronitrile,propyl chloride, isobutyl chloride, ethyl fluoride, ethyl bromide,n-pentyl iodide, ethyl dichloride, 2,3-dichlorobutane,1,3-dichlorobutane, 1,4- dichlorobutane, the chlorofluoroethanes, methylpentane, methylethyl ketone, diethyl ketone, n-butyl alcohol, methylpropionate, and the like. This invention is particularly adapted to thepreparation of vinylidene compounds containing at least one CHg=C groupthat is, a group containing a terminal methylene group attached by adouble bond to a carbon atom, and having 2 to 12 carbon atoms by thedehydrogenation of compounds of the formula CH3-CH3R where R is anorganic radical of from 0 to 10 carbon atoms, preferably formula CHEC-may be produced from the same starting materials.

Preferably oxygen is employed, suitably in an amount within the range of0.2 to about 5.0 mols of oxygen per mol of organic compound to bedehydrogenated, preferably from 0.2 to 2.5 moles per mole. Generally,better results may be obtained if the oxygen concentration is maintainedbetween about 0.25 and about 1.6 moles of oxygen per mole of organiccompound to be dehydrogenated, such as between 0.35 and 1.2 moles ofoxygen. The oxygen may be fed to the reactor as pure oxygen, as air, asoxygen-enriched air, oxygen mixed with diluents, and so forth. Based onthe total gaseous mixture entering the reactor, good results areobtained with oxygen present in an amount from about 0.5 to 25 volumepercent of the total gaseous mixture, such as in an amount from about 1to volume percent of the total. The total amount of oxygen utilized maybe introduced into the gaseous mixture entering the catalytic zone orsometimes it has been found desirable to add the oxygen in increments,such as to different sections of the reactor. The above describedproportions of oxygen employed are based on the total amount of oxygenused. The oxygen may be added directly to the reactor or it may beprem'ured, for example, with a diluent or steam. It is also within thescope of this invention to employ the described manganese compositionsas the partial or sole source of oxygen used for oxidativedehydrogenation. For example, the manganese compositions may releaseoxygen to react with the organic compound during a dehydrogenation stepand thereafter the manganese composition is regenerated by oxidationprior to another step where oxygen is released. Preferably such aprocess will have the manganese composition present as a moving bed.

It is one of the advantages of this invention that halo gen may also beadded to the reaction gases to give excellent results. The addition ofhalogen to the feed is particularly effective when the hydrocarbon to bedehydrogenated is saturated. The halogen present in the dehydrogenationzone may be either elemental halogen or any compound of halogen whichwould liberate halogen under the conditions of reaction. Suitablesources of halogen are such as hydrogen iodide, hydrogen bromide andhydrogen chloride; aliphatic halides, such as ethyl iodide, methylbromide, 1,2-dibromo ethane, ethyl bromide, amyl bromide, and allylbromide; cycloaliphatic halides, such as cyclohexylbromide; aromatichalides, such as benzyl bromide; halohydrins, such as ethylenebromohydrin; halogen substituted aliphatic acids, such as bromoaceticacid; ammonium iodide; ammonium bromide; ammonium chloride; organicamine halide salts, such as methyl amine hydrobromide; metal halidesincluding molten halides; and the like. Mixtures of various sources ofhalogen may be used. The preferred sources of halogen are iodine,bromine, and chlorine, and compounds there of, such as hydrogen bromide,hydrogen iodide, hydrogen chloride, ammonium bromide, ammonium iodide,ammonium chloride, alkyl halides of one to six carbon atoms and mixturesthereof, with the iodine and bromine compounds, especially the ammoniumcompounds, being particularly preferred. When terms such as halogenliberating materials or halogen materials are used in the specificationand claims, this includes any source of halogen such as elementalhalogens, hydrogen halides, or ammonium halides. The amount of halogen,calculated as elemental halogen, may be as little as about 00001 or lessmole of halogen per mole of the organic compound to be dehydrogenated toas high as 0.2 or 0.5. The preferred range is from about 0.001 to 0.09mole of halogen per mole of the organic compound to be dehydrogenated.

The temperature for the dehydrogenation reaction generally will be atleast about 250 C., such as greater than about 300 C. or 375 C., and themaximum temperature in the reactor may be about 650 C. or 750 C. orperhaps higher such as 900 C. under certain circumstances. However,excellent results are obtained within the range of about 300 C. to 575C., such as from or about 325 C. to or about 525 C. The temperatures aremeasured at the maximum temperature in the dehydrogenation zone. Anadvantage of this invention is that lower temperatures ofdehydrogenation may be utilized than are possible in conventionaldehydrogenation processes. Another advantage is that large quantities ofheat do not have to be added to the reaction.

The dehydrogenation reaction may be carried out at atmospheric pressure,superatmospheric pressure or at sub-atmospheric pressure. The totalpressure of the system will normally be about or in excess ofatmospheric pressure, although sub-atmospheric pressure may alsodesirably be used. Generally, the total pressure will be between about 4p.s.i.a. and about or p.s.i.a. Preferably, the total pressure will beless than about 75 p.s.i.a. and excellent results are obtained at aboutatmospheric pressure.

Preferably, the reaction mixture contains a quantity of steam, with therange generally being between about 2 and 40 moles of steam per mole oforganic compound to be dehydrogenated. Preferably, steam will be presentin an amount from about 3 to 35 moles per mole of organic compound to bedehydrogenated and excellent results have been obtained within the rangeof about 5 to about 30 moles of steam per mole of organic compound to bedehydrogenated. The functions of the steam are several-fold, and thesteam may not merely act as a diluent. Diluents generally may be used inthe same quantities as specified for the steam.

The gaseous reactants may be conducted through the reaction chamber at afairly wide range of flow rates. The optimum flow rate will be dependentupon such variables as the temperature of reaction, pressure, particlesize, and whether a fluid bed or fixed bed reactor is utilized.Desirable flow rates may be established by one skilled in the art.Generally, the flow rates will be within the range of about 0.10 to 25liquid volumes of the organic compound to be dehydrogenated per volumeof dehydrogenation zone containing catalyst per hour (referred to asLHSV), wherein the volumes of organic compound are calculated atstandard conditions of 0 C. and 760 mm. of mercury. Usually, the LHSVwill be between 0.15 and about 5 or 10. For calculation, the volume ofreactor containing catalyst is that volume of reactor space includingthe volume displayced by the catalyst. For example, if a reactor has aparticular volume of cubic feed of void space, when that void space isfilled with catalyst particles, the original void space is the volume ofreactor containing catalyst for the purpose of calculating the flowrate. The gaseous hourly space velocity (GHSV) is the volume of theorganic compound to be dehydrogenated in the form of vapor calculatedunder standard conditions of 0 C. and 760 mm. of mercury per volume ofreactor space containing catalyst per hour. Generally, the GHSV will bebetween about 25 and 6400 and excellent results have been obtainedbetween about 38 and 3800. Suitable contact times are, for example, fromabout 0.001 or higher to about 4 or 10 or 25 seconds, with particularlygood results being obtained between 0.01 and 5 seconds. The contact timeis the calculated dwell time of the reaction mixture in the reactionzone, assuming the moles of product mixture are equivalent to the molesof feed mixture. For the purpose of calculation of contact times, thereaction zone is the portion of the reactor containing catalyst which isat a temperature of at least 250 C.

The dehydrogenation reactor may be of the fixed bed or fluid bed type.Conventional reactors for the produc tion of unsaturated organiccompounds by dehydrogenation are satisfactory. Excellent results havebeen obtained by packing the reactor with catalyst particles as themethod of introducing the catalytic surface. The catalytic surface maybe introduced as such or it may be deposited on a carrier by methodsknown in the art such as by preparing an aqueous solution or dispersionof a catalytic material and mixing the carrier with the solution ordispersion until the active ingredients are coated on the carrier. If acarrier is utilized, very useful carriers are silicon carbide, aluminumoxide, pumice, and the like. Other known catalyst carriers may beemployed. When carriers are used, the amount of catalyst on the carrierwill suitably be between about to 75 weight percent of the total weightof the active catalytic material plus carrier. Another method forintroducing the required surface is to utilize as a reactor a smalldiameter tube wherein the tube wall is catalytic or is coated withcatalytic material. Other methods may be utilized to introduce thecatalytic surface such as by the use of rods, wires, mesh, or shreds,and the like, of catalytic material.

In the following examples the conversions, selectivities and yields arereported in mole percent. Otherwise, all percentages are weight percentunless expressed to the contrary. The apparatus used in the oxidativedehydrogenations consisted of a vertical fixed bed reactor containingthermocouples at spaced intervals throughout the bed. The temperaturereported for each dehydrogenation is the maximum temperature in the bed.The efiiuent from the reactor was condensed and analyzed immediately byvapor phase chromatography.

EXAMPLE 1 Catalyst preparation The catalysts were prepared from thequantities of starting materials described in Table I. The materialswere slurried together in distilled water for minutes using a one gallonWaring Blender. The slurry was dried in an oven at 100 C. The dried cakewas screened to remove particles larger than mesh and calcined in aVycor combustion tube (using a N atmosphere at 100 vols. of N /vol. ofcatalyst/hour) to the final calcination temperation (600 and 700 C.)recorded below and held at this temperature for 1 hour.

TABLE I Grams Cata- Cata- Materials lyst A lyst B 1. F9203 1 (86-88%F6203 Assay) 523. 2 523. 2 2. Manganous carbonate 2 (Assay 43.6% Mu)..-353. 5 353. 5 3. Manganous Chloride .(MI1Cl2 4H2O; assay 99 35. 9 35. 94. Chromium oxide 3 22. 8 22. 8 5. Distilled water 1,300 1,300 6. Carbonblack 0 50.0

A600 'B-60O A-700 B--700 The same amount of each catalyst was employedfor the runs in Example 2 in the reactor as described.

8 EXAMPLE 2 Oxidative dehydrogenation A feed of isoamylenes (85.4%2-methyl butene-l 0.7%-pentane, 2.9% isopentane, 2.8% other C and 0.1heavy ends) was fed at 1.5 LHSV, mole ratio of steam/ O /hydrocarbon of30/ .9/ 1. In Table II the catalysts, hours, maximum temperatures andresults are reported.

The catalyst loaded in the reactor and reduced for two hours at 840 F.with vols. of Hz/vol. of catalyst/hr.

After 97 hours on stream the hydrocarbon was discontinued and thecatalyst reduced at 840 F. for 2 hours with 100 vols. of Hz/VOL ofcatalyst/hr.

The invention claimed is:

1. An oxidative dehydrogenation catalyst consisting essentially of amanganese ferrite containing from 0.1 to 20 weight percent of intimatelymixed carbon black.

2. The catalyst according to claim 1 containing 1 to 15 weight percentcarbon black.

3. The catalyst according to claim 2 containing 2 to 10 weight percentcarbon black.

4. The process of preparing the catalyst of claim 1 wherein the carbonblack is intimately mixed with the precursors of the manganese ferriteand then reacting the precursors to form the manganese ferrite in anatmos phere containing less than 15 mole percent oxygen.

5. The process according to claim 4 wherein the atmosphere issubstantially free of oxygen.

6. The process according to claim 5 wherein the atmosphere comprisesnitrogen.

7. The process according to claim 5 wherein from 1 to 15 Weight percentcarbon black based on the total weight of the catalyst is added to themanganese ferrite precursors.

8. The process according to claim 7 wherein from 2 to 10 weight percentcarbon black based on the total weight of the catalyst is added to themanganese ferrite precursors.

References Cited UNITED STATES PATENTS 3,567,793 3/ 1971 Colling et al252-471 3,526,675 9/1970 Croce et al. 260-680 E 3,306,950 2/1967 .Bajarset al. 260-680 D 3,450,788 6/1969 Kehl et al 260-680 E 3,497,564 2/1970Allen et al. 252-447 2,683,123 7/1954 Schwegler et al. 252-470 3,205,1799/ 1965 Soderquist et al. 252-447 DANIEL E. WYMAN, Primary Examiner P.E. KONOPKA, Assistant Examiner US. Cl. X.R.

252-470, 471, 472; 260-666 A, 669 R, 673.5, 680 E, 669 R Po-ww 'UNITEDSTATES PATENT OFFICE (5/68)-- a QERHFICATE OF QQ ammo. 3 151,385 DatedAugust 7,1973

loventofls) Harold E. Manning I It is certified that error appears inthe above identified patent: and that said Letters Patent are herebycorrected as shown below:

v I H H E Col, 1, line 25 reads-" "-61-" but should read d-G groupingCol. 2, line 64 reads "wih $0 a" but should read 1% a Cole 4, line 20reads "-(zk-d k" but should read grouping,

Col. 4, line 43 reads."isobu$an e to'isobutyle" but should read"isobutane to isobutylene Col. 4, lille 74 reads "where" but should readwhereiu Col. 6, lines 2 and 3 read "of about" but should read of orabout "9 Col. 6, line 48 reads "displayced" but should read displacedCol. 7, 38 and 39 reads "tem-per ation'" but should read --;temperatureCol. 8, Table ll, heading "Hours on steam" should read Hours on streamSigned and sealed this 5th day of February 1974.,

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents

